vim-gitgutter
A Vim plugin which shows git diff markers in the sign column
...Beyond mere visual indicators, it also allows you to preview changes (“hunks”), stage or undo individual hunks (or even partial hunks), and jump between changed blocks of code. This tight integration with Git simplifies workflows, making it easier to review or commit changes without leaving the editor. Many users say it significantly improves productivity by reducing context switching: you see the effect of your edits in version-control terms right in your editor.